Visual search

The more distractors there are the harder it is to locate the letter B in the array

The O has a distinctive feature compared to the X and appears to "Pop Out" of the array

The red X is also a feature singleton and attracts attention

Conjunctive Search, find the orange square

Visual Search is an extension of attention and vigilance. Visual search involves and active scan of the environment for particular features. Such as trying to locate certain brand of cereal at the grocery store or a picture of a friend in a group photograph. The process of Visual Search is made more difficult through the occurrence of distracters. Distracters are non target stimuli that divert attention away from the target stimulus. False Alarms occur when we mistake a distracter for our target stimulus. In daily life marketers often take advantage of this by creating product packaging that closely resembles a more well known brand.

The number of distracters has an effect on how difficult or taxing the visual search task is. The size of a given visual array is commonly referred to is referred to the display size. The display size effect is the degree which the size of the display size hinders the visual search process. Depending on the type of visual search the display size can vary greatly.

Types of search

Feature Search

Feature Search is the process of searching for distinctive feature. Such as color, size, orientation or shape. Feature searches can sometimes be easily conducted if the target stimulus has a distinctive feature compared to its distracters. The object often appears to “pop out” of the display. A unique feature which causes a stimulus which to “pop out” is referred to as a feature singleton. Feature singletons can also attract attention even if they are distracters.

Conjunction Search

Conjunction Search occurs when a single feature search is in sufficient. In a conjunction search each item in the visual array must be examined to determine if it is the target stimulus. The number of distracters can greatly increase the search time in a conjunction search.

Popular Search Theories

• Feature Integration Theory
• Similarity Theory
• Guided Search Theory
• Movement Filter Theory
• Signal Detection Theory
• Search via recursive rejection
• Selective Attention For Identification Model

Bibliography

Reviews of the area

• Brodie, D. (1989)(Ed.), The First International Conference on Visual Search. London: Taylor Francis.
• Brodie, D. (1992)(Ed.), The Second International Conference on Visual Search. London: Taylor Francis.

Additional material – Papers

• Google Scholar
• Linnell, K. J. & Humphreys, G. W. (2002) Visual Search Within Versus Across Dimensions: A Case For Within-Dimension Grouping. British Journal Of Psychology, 93, 115-136.

• Olivers, C. N. L., Humphreys, G. W., Heinke, D. & Cooper, A. C. G.(2002) Prioritization In Visual Search: Visual Marking Is Not Dependent On A Mnemonic Search. Perception & Psychophysics 64 (4): 540-560.
• Jacobsen, T., Schroger, E., Humphreys, G. W. & Roeber, U. (2001) Facilitation of visual search at new positions: A behavioral and ERP study of new object capture. Neuroreport, 12, 4161-4164.
• Watson, D. G. & Humphreys, G. W. (1999). Segmentation on the basis of linear and local rotational motion: Motion grouping in visual search. Journal of Experimental Psychology: Human Perception and Performance, 25, 70-82
• Gilchrist, I., Humphreys, G. W., Riddoch, M. J. & Neumann, H. (1997). Luminance and edge information in grouping: A study using visual search. Journal of Experimental Psychology: Human Perception and Performance, 23, 464-480.
• Wolfe, J M (1998) Visual Search. Originally Published in , H. Pashler (Ed.)Attention, London, UK: University College London Press, Fulltext
• Smith, K. J. & Humphreys, G. W. (1995). Mechanisms of visual search: An implementation of guided search. In L. S. Smith & P. J. B. Hancock (Eds.), Neural Computation and Psychology. Springer: London.
• Duncan, J. & Humphreys, G. W. (1992) Beyond the search surface: Visual search and attentional engagement. Journal of Experimental Psychology: Human Perception and Performance, 18, 578-588.
• Humphreys, G. W., Freeman, T. & Muller, H. M. (1992) Lesioning a connectionist model of visual search: Selective effects on distractor grouping. Canadian Journal of Psychology, 46, 417-460.
• Muller, H. & Humphreys, G. W. (1992) A connectionist model of visual search. In D. Brodie (Ed.), The Second International Conference on Visual Search. London: Taylor Francis.
• Theeuwes J (1992) Perceptual selectivity for color and form. Perception & Psychophysics1992, 51(6), 599-606. Fulltext
• Treisman A (1991) Visual perception of features and objects. Annual Report, 15 Sep. 1990- 14.
• Duncan, J. & Humphreys, G. W. (1989) Visual search and stimulus similarity. Psychological Review, 96, 433-458.
• Verghese, P (2001) Visual Search and Attention: a Signal Detection Theory approach. Neuron, 30 August 2001, vol. 31, no. 4, pp. 523-535(13).